[Light- and electron microscope studies of human fetal membranes. 1. Amnion and intermediate layer]

In the course of a series of histiophysiological tests, a structural analysis was made of the different layers of foetal membranes. They were based on optical light and electron microscopy. Particular attention was given to the question for the secretory and resorptive faculties of this intermediate layer between the compartments of mother and amniotic fluid. --The first tests were made by means of amnion morphology, histochemistry, and thin-layer chromatography for the purpose of elucidating the composition of lipid droplets. Their form and chemical composition were both found to be similar to those of lipid droplets (liposomes) which were suspended in amniotic fluid. This fact, together with the morphological aspect, was likely to indicate hat the liposomes were expelled by exocytosis from amniotic epithelial cells. The endoplasmatic reticulum was active and granular, an indicator to sizeable formation of proteins in the amniotic epithelial cells. --Analysis by thin-layers chromatography showed lipids in both the amnion and amniotic fluid to consist of lysolecithin, sphingomyelin, phosphatidylserin, phosphatidylinosite, lecithin, kephalin, phosphatidyl-ethanolamine, cholesterinester, triglycerides, and sebacic acids. --The large intercellular spaces in the amniotic epithelium were found to form a labyrinth between surface differentiations of surrounding cell walls. There were numerous vesicles in the amniotic epithelial cells which were attributed to absorption of amniotic fluid from intercellular spaces as well as to its emission to cell surfaces. Some of the amniotic fluid was removed through the connective tissue of the amnion. Fibroblasts, located in connective tissue of the amnion, differed from connective tissue cells of adults, in that they were highly capable of synthesizing and storing both lipids and glycogen. They were also capable of meconium storage. Structures recorded by electron microscopy from the intermediate layer were safely identified as remnants of extraembryonic mesenchyma.